Digital video recorder (DVR), also called a personal video recorder (PVR), is a device that stores visual images and sound in digital (numerical) form. A typical DVR stores this digital data on a hard drive like that used in a personal computer. But some DVR’s store data on digital video tape.
A common type of DVR is connected to a cable television system for recording. Television programs are sent over traditional cable systems as high-frequency analog signals, which represent data as a continuously varying voltage. The tuner, an electronic circuit in the DVR, selects the desired program and converts it into an analog video signal. A device called an encoder then converts this signal into a digital signal, a code in the form of a sequence of high and low voltages. The encoder compresses the digital signal by removing repeated and unnecessary information and sends the compressed signal to the hard drive. The hard drives of some DVR’s can store 100 or more hours of compressed programs. During playback, the DVR converts the digital information back into an analog video signal and sends it to a conventional television receiver.
Because any region of a hard drive can be accessed quickly, a user can replay any part of a stored program almost instantly. A DVR also enables a user to begin playing back a program before it has finished recording. Some DVR’s are connected to a telephone line, through which they receive updates of TV program schedules from a service provider. Others receive updates directly from cable television systems. The first DVR’s for home use became available in 1999.
See also Videotape recorder.
